1. Field of the Invention
The invention comprises a movable fixture for rapidly preassembling electrical devices (packages) on a heat sink ready for insertion on a printed wiring board.
2. Background of the Art
In the assembly of electronic equipment, packaged electrical or electronic devices which generate significant amounts of heat are placed in physical contact with heat sinks. The packages of the electronic devices include a sealed plastic cover and a plurality of connection pins extending from the package. It is customary to first assemble the electrical devices in physical contact with the heat sink and then clamp them in place. The assembled electrical devices are connected to a printed wiring board (PWB) by inserting the connection pins from the electrical devices into corresponding connection openings for the pins in the electrical board for soldering the connection pins to electrical leads in the board. Electrical devices that are power supplies commonly require in relation to their size, substantial heat sinks to carry the heat away during use.
In an effort to increase productivity of assembly line workers, prior art has used jigs of the kind shown in FIG. 1 in order to preassemble electrical devices (packages) onto heat sinks. The prior art jig has a base supporting a plate with a configuration of pin openings for an arrangement of electrical devices. The heat sink is temporarily mounted vertically on the plate and has a horizontal threaded opening for a screw which is used to clamp the electrical devices in place. The electrical devices are placed against the heat sink surface or against an electrically insulating layer thereon with the connection pins positioned in the openings. Plate-like clamping devices are tightened while holding the electrical devices positioned in place against the surface of the heat sink with the aid of the pins positioned in the opening of the plate.
Frequently the packages to be clamped against the heat sink are different sizes. Often it is necessary to have packages with shorter bodies than the other packages elevated from the surface of the plate where they must be held in the elevated position while being clamped. This becomes a difficult proposition trying to manipulate the clamps and tighten the screws or bolts while holding the electrical devices in the proper position so that the electrical devices are accurately positioned on the heat sink. It is also important that the main axis of the device be parallel with the openings so that the devices are not tilted slightly. If the devices are tilted, a bad connection can result when the pins are soldered or otherwise electrically connected to the PWB. It becomes an extraordinarily difficult proposition if electrical devices are being assembled on both sides of the heat sink and it becomes necessary to loosen one of the bolts for adjustment of the devices on the previously clamped side for some reason. In any event, it is difficult under best conditions to manipulate the electrical devices into the best proper position even with the aid of the jig shown in FIG. 1 when the bolts and clamping devices are installed horizontally.